1. The Field of the Invention
The present invention is directed generally to a plural component spray gun. More specifically, the present invention is directed to an airless plural component spray gun capable of applying plural components without the additional equipment, e.g., air hoses, ports, compressor, etc., necessary to enable prior art applications, power sources to run such equipment and problems associated with using such equipment, e.g., overspray, maintenance costs, downtime and the like.
2. Background Art
Spray foam has been in use for about 50 years. Polyurea/urethane fast-set elastomeric coatings have been in use for about 20 years. For coatings and the like, two-part self-setting compounds may be mixed in a desired ratio and applied to the target surface or part. Compounds react quickly, yet the foam or coatings are sprayed at typically from 1-3 Gallons Per Minute (GPM). In most applications, the components mix within the plural component spray gun just before exiting to the target surface.
One of the biggest complaints about current spray foam equipment including the spray gun is that the equipment is difficult to learn to use, and is prone to failure due to too many electronics and related equipment that is not easy for the layman contractor/sprayer to troubleshoot and fix. Down time of spray foam equipment is costly, and can prevent timely completion of projects. Moreover, replacement parts are expensive and may require significant lead times to acquire.
Another problem in the industry is that most modern proportional spray foam systems do not provide the desired ratio of components, for example a 1:1 by volume ratio for the spray components. Typically, current systems therefore deliver a mixture that does not have the proper stoichiometry or the best physical properties of the components. Another disadvantage of prior art systems is that they frequently heat the components while they are still in the drum, which can cause problems. For example, heating the components prior to pumping will lower the viscosities and can cause striation, resulting in premature expansion of the B resin foam, which is then impractical to pump. The lowered viscosity may also cause leaking at the pump seals.
Yet another disadvantage of prior art systems is the use of pneumatic drive systems for the pumps, requiring a large volume of pressurized air. Suitable pneumatic systems are noisy, dirty and require larger air compressors.
Yet another disadvantage of prior art spray guns is the large number of parts required to enable spray gun and the large number of parts that must be disassembled for cleaning and reassembled.
Particular illustrative examples of applications for spray foam systems include, without limitation, (i) building insulation; (ii) roofing insulation; (iii) marine craft floatation material and motor vehicle crash space volumes; (iv) pipe insulation; (v) foam molding of parts, including for example wave boards; (vi) insulation for commercial freezers and refrigeration systems; (vii) commercial specialty building domes that are otherwise difficult to insulate; (viii) concrete leveling; (ix) prosthetic bones for training; (x) flotation items, including for example docks; (xi) props for type entertainment centers, for example fake rocks for resorts; (xii) military tent insulation; and the like.
Particular illustrative example of applications for polyurea/urethane elastomeric coatings include, without limitation: (i) floors; (ii) pickup truck bed liners; (iii) secondary containment, for example sewage clarifiers; (iv) military bullet proofing and bomb-fragment protection; (v) roof coatings; (vi) injection molding; and the like.
Both the spray foam industry and the polyurea/urethane elastomeric coatings industry use the same or similar equipment, and are collectively referred to herein as “spray foam equipment,” “spray system” or similar phraseology. Typically, polyurea/urethane elastomeric coatings simply use higher heat and pressure.
U.S. Pat. No. 7,694,893 to Zittel, et. al. (hereinafter Zittel) discloses a plural component spray gun designed for spraying quick setting materials such as foams, polyurea and the like. According to Zittel, its gun is designed so as to be easily serviceable with a minimum of tools. For example, the side seal cartridges may be installed and removed without tools by removing the retaining ring and then extracting them from the fluid housing. Those cartridges are purported to be easily disassembled and cleaned. Similarly, the fluid housing is purported to be removed from the handle/body by unscrewing the lock ring by hand. It shall be immediately appreciated that Zittel's spray gun includes numerous parts and operates with the aid of a supply of compressed air. Zittel's design therefore does not lend itself to easy dismantling, accounting of parts after Zittel's spray gun has been dismantled and reassembly of the parts after cleaning. A cleaning process for Zittel's spray gun is not only time consuming but is also a risky process where various parts may be lost or incorrectly reassembled.
U.S. Pat. No. 5,829,679 to Strong (hereinafter Strong) discloses a plural component airless spray gun for reactive liquid materials which has a mix chamber into which coreactive liquid components are introduced and mixed, an airless tip at a forward outlet from the chamber from which the mixed components are emitted in a fan-shaped spray, and a mechanically operated purge rod for cleaning residual reactants from the mix chamber and airless tip. The purge rod has a main body of a diameter slightly less than that of the mix chamber and a probe at its forward end that geometrically conforms to and is adapted to enter into and clean the inside of the spray tip. During spraying the purge rod is retracted in the mix chamber rearwardly of liquid reactant inlets to the chamber. As shown in Column 4 lines 35 to 45 of Strong below, Strong involves the use of an air cylinder although it is pitched as an airless spray gun:                “To turn the spray gun 20 on and off and to mechanically clean the mix chamber 68 and the interior of the airless tip 70 of residual reactive material upon termination of spraying, the spray gun has a purge rod 78. The purge rod extends forwardly into the mix chamber from a forward end of a drive rod 80 that is reciprocated in longitudinal directions by the air cylinder and piston assembly 24. The purge rod has a cylindrical main body 84 of a first diameter that makes a close sliding fit with the mix chamber. The purge rod also has a cylindrical part 86, for cleaning the airless tip passage 74, that extends forwardly from the main body 84.” (emphasis supplied)        
U.S. Pat. No. 4,453,670 to Sirovy (hereinafter Sirovy) discloses a plural component flushless spray gun which has a fluid outlet orifice defined by two opposed inlet orifices with a thin blade interposed therebetween. The blade prevents fluidic material exiting each inlet orifice from flowing directly into the other, and is slotted at its forward end to define a very small volume chamber into which the components flow for mixing prior to being emitted through the outlet orifice defined at the forward end of the slot. Because the chamber has a very small volume, the components are intimately mixed for better polymerization, and only a very small quantity of reactive components are mixed within the gun immediately behind the outlet orifice. Consequently, should the mixed components harden within the gun, only a limited amount of material is involved and the blockage may readily be removed simply by triggering the gun on to eject the blockage through the outlet orifice. The spray gun of Sirovy involves three mechanically moving valving rods with the center one having a blade in an attempt to get rid of the solvent used. Significant waste is generated as a result of the use of the solvent.
U.S. Pat. No. 3,606,170 to Hoffman, et. al. (hereinafter Hoffman) discloses a plural component spray gun which is utilized, for example, in the spraying of plastic foams. Pressurized fluid components flow through the spray gun where they are mixed together and discharged through a spray nozzle. The spray gun includes a spray head mounted on a spray gun body. The spray head defines a plurality of valve chambers which are located on longitudinally extending and parallel major axes. A valve assembly is positioned in each of the valve chambers and each of the valve assemblies includes a fluid discharge opening. A nozzle assembly, which includes a mixing plate is removably mounted on the front end of the spray head. The mixing plate is closely adjacent the discharge ends of the valve assemblies. The mixing plate defines a passageway network which is in communication with each of the fluid discharge openings. The plural components are fed through the passageway network upon the operation of a triggering apparatus. A second triggering apparatus is connected to another one of the valve assemblies and is utilized to direct solvent into the passageway network during the cleaning of the spray gun. In using Hoffman's spray gun, the spray gun is immediately purged with a third component, e.g., a solvent and therefore a container is required to collect this waste. This spray gun many work for very slow mixing components but significant waste disposal problems arise as a result of purging with a solvent.
Yet other types of spray guns have been attempted but all fail to satisfy consumer needs as the spray guns require the use of compressed air and the equipment associated with such use. Among spray guns which have been attempted but found to be undesirable, are those using air purge. The part count for such spray guns is numerous and the labor involved in cleaning such spray guns is tremendous.